The present invention relates to an expandable jaw broken bolt extractor for removing broken threaded fasteners, such as bolts, and in particular to an extractor designed to remove small diameter broken bolts which are difficult to grasp during the removal process.
Broken bolt extractors, which are commonly available for removing broken bolts from within a threaded bore, are often formed of a pointed tool having gripping teeth or shaped flutes which are structured to engage the sides of a bore drilled through the broken bolt. When the extractor is rotated in the opposite direction to that of the bolt threads, the gripping surfaces grip the internal walls of the bore and remove the broken bolt as the tool is rotated. One of the shortcomings of this type of extractor is for small broken bolt studs it is often difficult to have enough of a gripping surface between the broken stud and the tool to enable the tool to lock onto the stud for removal. This is because the tool frictionally engages only the upper rim surface near the outer edge of the bore and this area is simply not enough to cause the tool to lock on to the broken bolt stud.
With the present invention, an expandable jaw broken bolt extractor extends completely within the bore and during the extraction process resilient jaw members are expanded outwardly against the sides of the bore to provide an increased gripping area between the extractor tool and the broken bolt stud to ensure a solid non-slipping frictional engagement between the parts. Continued rotation of the tool then results in the removal of the broken stud.
The bolt extractor has a cylindrical body. One end serves as a drive means which may be a removable handle or may be an integrally formed hexagonal drive head which cooperates with a suitable hand or power tool, or a threaded hole in which a slide hammer can be installed. The cylindrical body includes threads (in the opposite direction to the threads on the broken stud to be extracted) which receive an expander collet having a plurality of resilient members extending downwardly and inwardly terminating in expansion fingers. The opposite end of the cylindrical body is formed with an expander which extends between the resilient members so that rotation of the cylindrical body in the collet causes the cylindrical body to move longitudinally along the threads. The expander on the cylindrical body moves the fingers of the collet outwardly and as the fingers move apart they engage interior walls of the bore in the broken bolt stud until a firm grip is formed. Continued rotation of the cylindrical body results in a firmer grip between the gripping fingers and the broken bolt stud, permitting removal of the stud.
Among the objects of the present invention is the provision of a broken bolt fastener extractor tool suitable for moving small diameter broken bolts and the provision of a broken bolt extractor tool providing an improved gripping means to engage the broken stud during the removal process.